Mechanisms for photo assisted Fenton of synthesized pyrrhotite at neutral pH
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The self-induced flotation behavior of pyrrhotite was investigated in this paper. The potential-pH ranger for pyrrhotite flotation was determined. It was been shown that pyrrhotite exhibit good self - induced floatability. With the variation of pH , the upper or lower limit of pyrrhotite flotation is different. Reaction mechanism of the surface oxidation for pyrrhotite was studied by using cyclic voltammetric measurements. E-pH diagram was constructued for pyrrhotite oxidation. The elemental sulphur was identified to be primary hydrophobic entity on pyrrhotite.
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The nonstoichiometric sulfide pyrrhotite (Fe S) common to many ore deposits occurs in a variety of crystallographic forms and compositions and occasionally is also intergrown with stoichiometric troilite (FeS). In this study, the mineralogy of pyrrhotite derived from several different nickel and PGE ore deposits in South Africa, Botswana, and Canada was examined in detail in terms of pyrrhotite association, crystallography, and mineral chemistry. Pyrrhotite samples were subdivided into two-phase 6C Fe11S12 pyrrhotite intergrown with2C FeS troilite, two-phase 4C Fe7S8 pyrrhotite intergrown with 5C Fe9S10 pyrrhotite, single-phase 5C Fe9S10 pyrrhotite and single-phase 4C Fe7S8 pyrrhotite. None of the pyrrhotite samples analyzed were classified as two-phase 4C pyrrhotite intergrown with pyrite due to the scarcity of pyrite in these samples. Average solid solution Ni contents of NC pyrrhotite (0.75 ± 0.10 wt % Ni) in this study were found to be greater than in 4C pyrrhotite (0.43 ± 0.10 wt % Ni), but only when the pyrrhotite occurred as two-phase 4C pyrrhotite intergrown with NC pyrrhotite. For single-phase pyrrhotite occurrences in this study, 4C pyrrhotite was more Ni rich (up to 2 wt % Ni) than NC pyrrhotite (0.75 ± 0.19 wt % Ni). The average atomic metal/S ratios obtained for 4C Fe7S8 pyrrhotite was 0.869 ± 0.013 (n = 699), for 5C Fe9S10 pyrrhotite was 0.895 ± 0.013 (n = 316) and for 6C Fe11S12 pyrrhotite was 0.918 ± 0.017 (n = 101). The histogram comparing metal/S ratios of all the pyrrhotite samples analyzed showed a continuum of metal/S ratios, although with frequency maxima corresponding to the ideal compositions of 4C, 5C, and 6C pyrrhotite. The presence of the continuum however, was interpreted to be representative of nonstoichiometry in the pyrrhotite structure.
Troilite
Pentlandite
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Xanthate
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The Journal of the Japanese Association of Mineralogists Petrologists and Economic Geologists (1962)
Pyrrhotite is a relatively high temperature mineral and occurs in association with other high ordinary minerals. The writer studied the properties of pyrrhotites in Japan with special reference to the relation between α-pyrrhotite and β-pyrrhotite with the change of chemical composition. The main results obtained are as follows: (1) Pyrrhotite can be classified into the following three types according to the physico-chemical properties: (a) α-pyrrhotite (b) β-pyrrhotite (c) α+β-pyrrhotite (2) α-pyrrhotite is peak type at the magnetism and β-pyrrhotite is Weiss type. (3) α+β type pyrrhotite is a mechanical mixture of α-pyrrhotite and β-pyrrhotite and may be appear to be lamellae textures Zerknitterungs Lamelle (4) Zerknitterungs Lamelle texture is often observed in the Kieslager type deposits, but it is not so common in the vein and replacement deposits. (5) The writer, as well as many other investigators believes that nonhomogenity of pyrrhotite caused by the variation of Fe: S ratio and Zerknitterungs Lamelle texture are interpreted as the result of exsolution of solid solution or thermal metamorphic differentiation.
Texture (cosmology)
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Xanthate
Sulfide Minerals
Stoichiometry
Magnetic separation
Froth flotation
Pentlandite
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Troilite
Inert gas
Inert
Greigite
Iron sulfide
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Fugacity
Mineral redox buffer
Sulfide Minerals
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The non-stoichiometric sulfi de mineral pyrrhotite (Fe(1-x)S), common to many nickel ore deposits, occurs in a variety of crystallographic forms, each with subtly differing physical and chemical properties. Since there appears to be little agreement in the literature as to how these varying properties infl uence the reactivity and fl otation performance of pyrrhotite, the manipulation of pyrrhotite fl otation performance is not necessarily simple, especially since there is no uniformity as to whether pyrrhotite is recovered or rejected during fl otation. Using nickeliferous pyrrhotite samples derived from the Nkomati ore in South Africa, Phoenix ore in Botswana and Sudbury ore in Canada, the mineralogy and reactivity of magnetic (Fe7S8), non-magnetic (Fe9S10) and inter grown magnetic and non-magnetic pyrrhotite was characterised and the relationship to fl otation performance developed. Rest potential, cyclic voltammetry and oxygen uptake measurements were used to quantify the reactivity of pyrrhotite and demonstrated that magnetic pyrrhotite was the most reactive, whereas non-magnetic pyrrhotite was relatively unreactive. In some scenarios, the magnetic pyrrhotite was so reactive it was already passivated and appeared to be relatively unreactive. Subsequent microfl otation tests showed that the relatively unreactive non-magnetic pyrrhotite had the best collectorless fl otation recovery and that only with the addition of reagents could differences in the fl otation performance of magnetic and mixed pyrrhotite samples be identifi ed. These differences in pyrrhotite fl otation performance were primarily attributed to the propensity of the different pyrrhotite samples for oxidation and formation of hydrophilic ferric hydroxides. In turn, this was evaluated according to the effect that pyrrhotite crystallography, mineral chemistry and mineral association have in controlling the surface characteristics of pyrrhotite and its subsequent fl otation performance. This study has clearly demonstrated the importance of mineralogy as a tool to understand pyrrhotite fl otation performance which may be utilised for plant optimisation.
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Roasting reaction of pyrrhotite and its reaction rates at various temperatures were studied by means of a thermo-balance in order to obtain a better understanding of the roastability of pyrrhotite.Pyrrhotite reacted with air to from an oxide at temperatures above 550°, but the reaction rate was slow. At temperatures between 230° and 550°,it reacted with air to form a sulpate. This sulphate, furthermore, obstructed the reaction of the oxide formation at temperatures above 550°. Consequently, the roastability of pyrrhotite was considerably lower than that of pyrite. The fine particles of the natural pyrrhotite temporarily showed a rapid decrease in weight due to the oxide formation at 405°. The roastability of the natural pyrrhotite was, therefore, higher than that of the compound one (FeS). The coarse particles of the natural pyrrhotite, however,did not show any decrease in weight at 405°. The fast air flow transferred the rapid decrease in weight, whiich took place at 405°,to a higher temperature and did not improve the roastability of pyrrhotite,although it slightly accelerated the reaction rate of the oxide formation.
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